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				4	<head>
				5	<title>LLVM Programmer's Manual</title>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	6	<link rel="stylesheet" href="llvm.css" type="text/css">
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	7	</head>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	8	<body>
				9
				10	<div class="doc_title">
				11	LLVM Programmer's Manual
				12	</div>
				13
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	14	<ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	15	<li><a href="#introduction">Introduction</a></li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	16	<li><a href="#general">General Information</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	17	<ul>
				18	<li><a href="#stl">The C++ Standard Template Library</a><!--
Chris Lattner	986e0c9	2002-09-22 19:38:40 +0000	[diff] [blame]	19	<li>The <tt>-time-passes</tt> option
				20	<li>How to use the LLVM Makefile system
				21	<li>How to write a regression test
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	22	--> </li>
Chris Lattner	84b7f8d	2003-08-01 22:20:59 +0000	[diff] [blame]	23	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	24	</li>
				25	<li><a href="#apis">Important and useful LLVM APIs</a>
				26	<ul>
				27	<li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt>
				28	and <tt>dyn_cast<></tt> templates</a> </li>
				29	<li><a href="#DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt>
				30	option</a>
				31	<ul>
				32	<li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
				33	and the <tt>-debug-only</tt> option</a> </li>
				34	</ul>
				35	</li>
				36	<li><a href="#Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				37	option</a><!--
Chris Lattner	986e0c9	2002-09-22 19:38:40 +0000	[diff] [blame]	38	<li>The <tt>InstVisitor</tt> template
				39	<li>The general graph API
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	40	--> </li>
				41	</ul>
				42	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	43	<li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	44	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	45	<li><a href="#inspection">Basic Inspection and Traversal Routines</a>
				46	<ul>
				47	<li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
				48	in a <tt>Function</tt></a> </li>
				49	<li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
				50	in a <tt>BasicBlock</tt></a> </li>
				51	<li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
				52	in a <tt>Function</tt></a> </li>
				53	<li><a href="#iterate_convert">Turning an iterator into a
				54	class pointer</a> </li>
				55	<li><a href="#iterate_complex">Finding call sites: a more
				56	complex example</a> </li>
				57	<li><a href="#calls_and_invokes">Treating calls and invokes
				58	the same way</a> </li>
				59	<li><a href="#iterate_chains">Iterating over def-use &
				60	use-def chains</a> </li>
				61	</ul>
				62	</li>
				63	<li><a href="#simplechanges">Making simple changes</a>
				64	<ul>
				65	<li><a href="#schanges_creating">Creating and inserting new
				66	<tt>Instruction</tt>s</a> </li>
				67	<li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
				68	<li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
				69	with another <tt>Value</tt></a> </li>
				70	</ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	71	<!--
				72	<li>Working with the Control Flow Graph
				73	<ul>
				74	<li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
				75	<li>
				76	<li>
				77	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	78	--> </li>
				79	</ul>
				80	</li>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	81	<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	82	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	83	<li><a href="#Value">The <tt>Value</tt> class</a>
				84	<ul>
				85	<li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	86	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	87	<li><a href="#Instruction">The <tt>Instruction</tt> class</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	88	<ul>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame^]	89	<li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt>
				90	class</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	91	</ul></li>
				92	<li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
				93	<ul>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame^]	94	<li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
				95	<li><a href="#Function">The <tt>Function</tt> class</a></li>
				96	<li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class
				97	</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	98	</ul></li>
				99	<li><a href="#Module">The <tt>Module</tt> class</a></li>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame^]	100	<li><a href="#Constant">The <tt>Constant</tt> class</a></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	101	<li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame^]	102	<li><a href="#Argument">The <tt>Argument</tt> class</a></li>
				103	</ul></li>
				104	</ul></li>
				105	<li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
				106	<li>The <tt>ilist</tt> and <tt>iplist</tt> classes
				107	<ul>
				108	<li>Creating, inserting, moving and deleting from LLVM lists </li>
				109	</ul>
				110	</li>
				111	<li>Important iterator invalidation semantics to be aware of.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	112	</li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	113	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	114
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	115	<div class="doc_author">
				116	<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
				117	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>, and
				118	<a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	119	</div>
				120
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	121	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	122	<div class="doc_section">
				123	<a name="introduction">Introduction </a>
				124	</div>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	125	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	126
				127	<div class="doc_text">
				128
				129	<p>This document is meant to highlight some of the important classes and
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	130	interfaces available in the LLVM source-base. This manual is not
				131	intended to explain what LLVM is, how it works, and what LLVM code looks
				132	like. It assumes that you know the basics of LLVM and are interested
				133	in writing transformations or otherwise analyzing or manipulating the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	134	code.</p>
				135
				136	<p>This document should get you oriented so that you can find your
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	137	way in the continuously growing source code that makes up the LLVM
				138	infrastructure. Note that this manual is not intended to serve as a
				139	replacement for reading the source code, so if you think there should be
				140	a method in one of these classes to do something, but it's not listed,
				141	check the source. Links to the <a href="/doxygen/">doxygen</a> sources
				142	are provided to make this as easy as possible.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	143
				144	<p>The first section of this document describes general information that is
				145	useful to know when working in the LLVM infrastructure, and the second describes
				146	the Core LLVM classes. In the future this manual will be extended with
				147	information describing how to use extension libraries, such as dominator
				148	information, CFG traversal routines, and useful utilities like the <tt><a
				149	href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
				150
				151	</div>
				152
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	153	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	154	<div class="doc_section">
				155	<a name="general">General Information</a>
				156	</div>
				157	<!-- *********************************************************************** -->
				158
				159	<div class="doc_text">
				160
				161	<p>This section contains general information that is useful if you are working
				162	in the LLVM source-base, but that isn't specific to any particular API.</p>
				163
				164	</div>
				165
				166	<!-- ======================================================================= -->
				167	<div class="doc_subsection">
				168	<a name="stl">The C++ Standard Template Library</a>
				169	</div>
				170
				171	<div class="doc_text">
				172
				173	<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	174	perhaps much more than you are used to, or have seen before. Because of
				175	this, you might want to do a little background reading in the
				176	techniques used and capabilities of the library. There are many good
				177	pages that discuss the STL, and several books on the subject that you
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	178	can get, so it will not be discussed in this document.</p>
				179
				180	<p>Here are some useful links:</p>
				181
				182	<ol>
				183
				184	<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
				185	reference</a> - an excellent reference for the STL and other parts of the
				186	standard C++ library.</li>
				187
				188	<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
				189	O'Reilly book in the making. It has a decent <a
				190	href="http://www.tempest-sw.com/cpp/ch13-libref.html">Standard Library
				191	Reference</a> that rivals Dinkumware's, and is actually free until the book is
				192	published.</li>
				193
				194	<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
				195	Questions</a></li>
				196
				197	<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
				198	Contains a useful <a
				199	href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
				200	STL</a>.</li>
				201
				202	<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
				203	Page</a></li>
				204
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame^]	205	<li><a href="http://www.linux.com.cn/Bruce_Eckel/TICPPv2/Contents.htm">
				206	Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
				207	the book).</a></li>
				208
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	209	</ol>
				210
				211	<p>You are also encouraged to take a look at the <a
				212	href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
				213	to write maintainable code more than where to put your curly braces.</p>
				214
				215	</div>
				216
				217	<!-- ======================================================================= -->
				218	<div class="doc_subsection">
				219	<a name="stl">Other useful references</a>
				220	</div>
				221
				222	<div class="doc_text">
				223
				224	<p>LLVM is currently using CVS as its source versioning system. You may find
				225	this reference handy:</p>
				226
				227	<ol>
				228	<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	229	Branch and Tag Primer</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	230	</ol>
				231
				232	</div>
				233
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	234	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	235	<div class="doc_section">
				236	<a name="apis">Important and useful LLVM APIs</a>
				237	</div>
				238	<!-- *********************************************************************** -->
				239
				240	<div class="doc_text">
				241
				242	<p>Here we highlight some LLVM APIs that are generally useful and good to
				243	know about when writing transformations.</p>
				244
				245	</div>
				246
				247	<!-- ======================================================================= -->
				248	<div class="doc_subsection">
				249	<a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
				250	</div>
				251
				252	<div class="doc_text">
				253
				254	<p>The LLVM source-base makes extensive use of a custom form of RTTI.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	255	These templates have many similarities to the C++ <tt>dynamic_cast<></tt>
				256	operator, but they don't have some drawbacks (primarily stemming from
				257	the fact that <tt>dynamic_cast<></tt> only works on classes that
				258	have a v-table). Because they are used so often, you must know what they
				259	do and how they work. All of these templates are defined in the <a
				260	href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	261	file (note that you very rarely have to include this file directly).</p>
				262
				263	<dl>
				264	<dt><tt>isa<></tt>: </dt>
				265
				266	<dd>The <tt>isa<></tt> operator works exactly like the Java
				267	"<tt>instanceof</tt>" operator. It returns true or false depending on whether
				268	a reference or pointer points to an instance of the specified class. This can
				269	be very useful for constraint checking of various sorts (example below).</dd>
				270
				271	<dt><tt>cast<></tt>: </dt>
				272
				273	<dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
				274	converts a pointer or reference from a base class to a derived cast, causing
				275	an assertion failure if it is not really an instance of the right type. This
				276	should be used in cases where you have some information that makes you believe
				277	that something is of the right type. An example of the <tt>isa<></tt>
				278	and <tt>cast<></tt> template is:
				279
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	280	<pre>
				281	static bool isLoopInvariant(const <a href="#Value">Value</a> V, const Loop L) {
				282	if (isa<<a href="#Constant">Constant</a>>(V) \|\| isa<<a href="#Argument">Argument</a>>(V) \|\| isa<<a href="#GlobalValue">GlobalValue</a>>(V))
				283	return true;
				284
				285	<i>// Otherwise, it must be an instruction...</i>
				286	return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
				287	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	288
				289	<p>Note that you should <b>not</b> use an <tt>isa<></tt> test followed
				290	by a <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt>
				291	operator.</p>
				292
				293	</dd>
				294
				295	<dt><tt>dyn_cast<></tt>:</dt>
				296
				297	<dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
				298	checks to see if the operand is of the specified type, and if so, returns a
				299	pointer to it (this operator does not work with references). If the operand is
				300	not of the correct type, a null pointer is returned. Thus, this works very
				301	much like the <tt>dynamic_cast</tt> operator in C++, and should be used in the
				302	same circumstances. Typically, the <tt>dyn_cast<></tt> operator is used
				303	in an <tt>if</tt> statement or some other flow control statement like this:
				304
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	305	<pre>
				306	if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
				307	...
				308	}
				309	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	310
				311	<p> This form of the <tt>if</tt> statement effectively combines together a
				312	call to <tt>isa<></tt> and a call to <tt>cast<></tt> into one
				313	statement, which is very convenient.</p>
				314
				315	<p> Another common example is:</p>
				316
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	317	<pre>
				318	<i>// Loop over all of the phi nodes in a basic block</i>
				319	BasicBlock::iterator BBI = BB->begin();
				320	for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast<<a href="#PHINode">PHINode</a>>(BBI); ++BBI)
				321	std::cerr << *PN;
				322	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	323
				324	<p>Note that the <tt>dyn_cast<></tt> operator, like C++'s
				325	<tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused.
				326	In particular you should not use big chained <tt>if/then/else</tt> blocks to
				327	check for lots of different variants of classes. If you find yourself
				328	wanting to do this, it is much cleaner and more efficient to use the
				329	InstVisitor class to dispatch over the instruction type directly.</p>
				330
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	331	</dd>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	332
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	333	<dt><tt>cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	334
				335	<dd>The <tt>cast_or_null<></tt> operator works just like the
				336	<tt>cast<></tt> operator, except that it allows for a null pointer as
				337	an argument (which it then propagates). This can sometimes be useful,
				338	allowing you to combine several null checks into one.</dd>
				339
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	340	<dt><tt>dyn_cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	341
				342	<dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
				343	<tt>dyn_cast<></tt> operator, except that it allows for a null pointer
				344	as an argument (which it then propagates). This can sometimes be useful,
				345	allowing you to combine several null checks into one.</dd>
				346
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	347	</dl>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	348
				349	<p>These five templates can be used with any classes, whether they have a
				350	v-table or not. To add support for these templates, you simply need to add
				351	<tt>classof</tt> static methods to the class you are interested casting
				352	to. Describing this is currently outside the scope of this document, but there
				353	are lots of examples in the LLVM source base.</p>
				354
				355	</div>
				356
				357	<!-- ======================================================================= -->
				358	<div class="doc_subsection">
				359	<a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
				360	</div>
				361
				362	<div class="doc_text">
				363
				364	<p>Often when working on your pass you will put a bunch of debugging printouts
				365	and other code into your pass. After you get it working, you want to remove
				366	it... but you may need it again in the future (to work out new bugs that you run
				367	across).</p>
				368
				369	<p> Naturally, because of this, you don't want to delete the debug printouts,
				370	but you don't want them to always be noisy. A standard compromise is to comment
				371	them out, allowing you to enable them if you need them in the future.</p>
				372
				373	<p>The "<tt><a href="/doxygen/Debug_8h-source.html">Support/Debug.h</a></tt>"
				374	file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
				375	this problem. Basically, you can put arbitrary code into the argument of the
				376	<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
				377	tool) is run with the '<tt>-debug</tt>' command line argument:</p>
				378
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	379	<pre> ... <br> DEBUG(std::cerr << "I am here!\n");<br> ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	380
				381	<p>Then you can run your pass like this:</p>
				382
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	383	<pre> $ opt < a.bc > /dev/null -mypass<br> <no output><br> $ opt < a.bc > /dev/null -mypass -debug<br> I am here!<br> $<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	384
				385	<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
				386	to not have to create "yet another" command line option for the debug output for
				387	your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
				388	so they do not cause a performance impact at all (for the same reason, they
				389	should also not contain side-effects!).</p>
				390
				391	<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
				392	enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
				393	"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
				394	program hasn't been started yet, you can always just run it with
				395	<tt>-debug</tt>.</p>
				396
				397	</div>
				398
				399	<!-- _______________________________________________________________________ -->
				400	<div class="doc_subsubsection">
				401	<a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE()</tt> and
				402	the <tt>-debug-only</tt> option</a>
				403	</div>
				404
				405	<div class="doc_text">
				406
				407	<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
				408	just turns on <b>too much</b> information (such as when working on the code
				409	generator). If you want to enable debug information with more fine-grained
				410	control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
				411	option as follows:</p>
				412
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	413	<pre> ...<br> DEBUG(std::cerr << "No debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "foo"<br> DEBUG(std::cerr << "'foo' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "bar"<br> DEBUG(std::cerr << "'bar' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE ""<br> DEBUG(std::cerr << "No debug type (2)\n");<br> ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	414
				415	<p>Then you can run your pass like this:</p>
				416
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	417	<pre> $ opt < a.bc > /dev/null -mypass<br> <no output><br> $ opt < a.bc > /dev/null -mypass -debug<br> No debug type<br> 'foo' debug type<br> 'bar' debug type<br> No debug type (2)<br> $ opt < a.bc > /dev/null -mypass -debug-only=foo<br> 'foo' debug type<br> $ opt < a.bc > /dev/null -mypass -debug-only=bar<br> 'bar' debug type<br> $<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	418
				419	<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
				420	a file, to specify the debug type for the entire module (if you do this before
				421	you <tt>#include "Support/Debug.h"</tt>, you don't have to insert the ugly
				422	<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
				423	"bar", because there is no system in place to ensure that names do not
				424	conflict. If two different modules use the same string, they will all be turned
				425	on when the name is specified. This allows, for example, all debug information
				426	for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	427	even if the source lives in multiple files.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	428
				429	</div>
				430
				431	<!-- ======================================================================= -->
				432	<div class="doc_subsection">
				433	<a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				434	option</a>
				435	</div>
				436
				437	<div class="doc_text">
				438
				439	<p>The "<tt><a
				440	href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>" file
				441	provides a template named <tt>Statistic</tt> that is used as a unified way to
				442	keep track of what the LLVM compiler is doing and how effective various
				443	optimizations are. It is useful to see what optimizations are contributing to
				444	making a particular program run faster.</p>
				445
				446	<p>Often you may run your pass on some big program, and you're interested to see
				447	how many times it makes a certain transformation. Although you can do this with
				448	hand inspection, or some ad-hoc method, this is a real pain and not very useful
				449	for big programs. Using the <tt>Statistic</tt> template makes it very easy to
				450	keep track of this information, and the calculated information is presented in a
				451	uniform manner with the rest of the passes being executed.</p>
				452
				453	<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
				454	it are as follows:</p>
				455
				456	<ol>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	457	<li>Define your statistic like this:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	458	<pre>static Statistic<> NumXForms("mypassname", "The # of times I did stuff");<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	459
				460	<p>The <tt>Statistic</tt> template can emulate just about any data-type,
				461	but if you do not specify a template argument, it defaults to acting like
				462	an unsigned int counter (this is usually what you want).</p></li>
				463
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	464	<li>Whenever you make a transformation, bump the counter:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	465	<pre> ++NumXForms; // I did stuff<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	466	</li>
				467	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	468
				469	<p>That's all you have to do. To get '<tt>opt</tt>' to print out the
				470	statistics gathered, use the '<tt>-stats</tt>' option:</p>
				471
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	472	<pre> $ opt -stats -mypassname < program.bc > /dev/null<br> ... statistic output ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	473
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	474	<p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
				475	suite, it gives a report that looks like this:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	476
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	477	<pre> 7646 bytecodewriter - Number of normal instructions<br> 725 bytecodewriter - Number of oversized instructions<br> 129996 bytecodewriter - Number of bytecode bytes written<br> 2817 raise - Number of insts DCEd or constprop'd<br> 3213 raise - Number of cast-of-self removed<br> 5046 raise - Number of expression trees converted<br> 75 raise - Number of other getelementptr's formed<br> 138 raise - Number of load/store peepholes<br> 42 deadtypeelim - Number of unused typenames removed from symtab<br> 392 funcresolve - Number of varargs functions resolved<br> 27 globaldce - Number of global variables removed<br> 2 adce - Number of basic blocks removed<br> 134 cee - Number of branches revectored<br> 49 cee - Number of setcc instruction eliminated<br> 532 gcse - Number of loads removed<br> 2919 gcse - Number of instructions removed<br> 86 indvars - Number of canonical indvars added<br> 87 indvars - Number of aux indvars removed<br> 25 instcombine - Number of dead inst eliminate<br> 434 instcombine - Number of insts combined<br> 248 licm - Number of load insts hoisted<br> 1298 licm - Number of insts hoisted to a loop pre-header<br> 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)<br> 75 mem2reg - Number of alloca's promoted<br> 1444 cfgsimplify - Number of blocks simplified<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	478
				479	<p>Obviously, with so many optimizations, having a unified framework for this
				480	stuff is very nice. Making your pass fit well into the framework makes it more
				481	maintainable and useful.</p>
				482
				483	</div>
				484
				485	<!-- *********************************************************************** -->
				486	<div class="doc_section">
				487	<a name="common">Helpful Hints for Common Operations</a>
				488	</div>
				489	<!-- *********************************************************************** -->
				490
				491	<div class="doc_text">
				492
				493	<p>This section describes how to perform some very simple transformations of
				494	LLVM code. This is meant to give examples of common idioms used, showing the
				495	practical side of LLVM transformations. <p> Because this is a "how-to" section,
				496	you should also read about the main classes that you will be working with. The
				497	<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
				498	and descriptions of the main classes that you should know about.</p>
				499
				500	</div>
				501
				502	<!-- NOTE: this section should be heavy on example code -->
				503	<!-- ======================================================================= -->
				504	<div class="doc_subsection">
				505	<a name="inspection">Basic Inspection and Traversal Routines</a>
				506	</div>
				507
				508	<div class="doc_text">
				509
				510	<p>The LLVM compiler infrastructure have many different data structures that may
				511	be traversed. Following the example of the C++ standard template library, the
				512	techniques used to traverse these various data structures are all basically the
				513	same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
				514	method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
				515	function returns an iterator pointing to one past the last valid element of the
				516	sequence, and there is some <tt>XXXiterator</tt> data type that is common
				517	between the two operations.</p>
				518
				519	<p>Because the pattern for iteration is common across many different aspects of
				520	the program representation, the standard template library algorithms may be used
				521	on them, and it is easier to remember how to iterate. First we show a few common
				522	examples of the data structures that need to be traversed. Other data
				523	structures are traversed in very similar ways.</p>
				524
				525	</div>
				526
				527	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	528	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	529	<a name="iterate_function">Iterating over the </a><a
				530	href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
				531	href="#Function"><tt>Function</tt></a>
				532	</div>
				533
				534	<div class="doc_text">
				535
				536	<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
				537	transform in some way; in particular, you'd like to manipulate its
				538	<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
				539	the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
				540	an example that prints the name of a <tt>BasicBlock</tt> and the number of
				541	<tt>Instruction</tt>s it contains:</p>
				542
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	543	<pre> // func is a pointer to a Function instance<br> for (Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {<br><br> // print out the name of the basic block if it has one, and then the<br> // number of instructions that it contains<br><br> cerr << "Basic block (name=" << i->getName() << ") has " <br> << i->size() << " instructions.\n";<br> }<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	544
				545	<p>Note that i can be used as if it were a pointer for the purposes of
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	546	invoking member functions of the <tt>Instruction</tt> class. This is
				547	because the indirection operator is overloaded for the iterator
Chris Lattner	7496ec5	2003-08-05 22:54:23 +0000	[diff] [blame]	548	classes. In the above code, the expression <tt>i->size()</tt> is
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	549	exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
				550
				551	</div>
				552
				553	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	554	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	555	<a name="iterate_basicblock">Iterating over the </a><a
				556	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				557	href="#BasicBlock"><tt>BasicBlock</tt></a>
				558	</div>
				559
				560	<div class="doc_text">
				561
				562	<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
				563	easy to iterate over the individual instructions that make up
				564	<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
				565	a <tt>BasicBlock</tt>:</p>
				566
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	567	<pre> // blk is a pointer to a BasicBlock instance<br> for (BasicBlock::iterator i = blk->begin(), e = blk->end(); i != e; ++i)<br> // the next statement works since operator<<(ostream&,...) <br> // is overloaded for Instruction&<br> cerr << *i << "\n";<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	568
				569	<p>However, this isn't really the best way to print out the contents of a
				570	<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
				571	anything you'll care about, you could have just invoked the print routine on the
				572	basic block itself: <tt>cerr << *blk << "\n";</tt>.</p>
				573
				574	<p>Note that currently operator<< is implemented for <tt>Value*</tt>, so
				575	it will print out the contents of the pointer, instead of the pointer value you
				576	might expect. This is a deprecated interface that will be removed in the
				577	future, so it's best not to depend on it. To print out the pointer value for
				578	now, you must cast to <tt>void*</tt>.</p>
				579
				580	</div>
				581
				582	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	583	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	584	<a name="iterate_institer">Iterating over the </a><a
				585	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				586	href="#Function"><tt>Function</tt></a>
				587	</div>
				588
				589	<div class="doc_text">
				590
				591	<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
				592	<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
				593	<tt>InstIterator</tt> should be used instead. You'll need to include <a
				594	href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
				595	and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	596	small example that shows how to dump all instructions in a function to the standard error stream:<p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	597
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	598	<pre>#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"<br>...<br>// Suppose F is a ptr to a function<br>for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)<br> cerr << *i << "\n";<br></pre>
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	599	Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
				600	worklist with its initial contents. For example, if you wanted to
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	601	initialize a worklist to contain all instructions in a <tt>Function</tt>
				602	F, all you would need to do is something like:
				603	<pre>std::set<Instruction*> worklist;<br>worklist.insert(inst_begin(F), inst_end(F));<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	604
				605	<p>The STL set <tt>worklist</tt> would now contain all instructions in the
				606	<tt>Function</tt> pointed to by F.</p>
				607
				608	</div>
				609
				610	<!-- _______________________________________________________________________ -->
				611	<div class="doc_subsubsection">
				612	<a name="iterate_convert">Turning an iterator into a class pointer (and
				613	vice-versa)</a>
				614	</div>
				615
				616	<div class="doc_text">
				617
				618	<p>Sometimes, it'll be useful to grab a reference (or pointer) to a class
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	619	instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	620	a reference or a pointer from an iterator is very straight-forward.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	621	Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	622	is a <tt>BasicBlock::const_iterator</tt>:</p>
				623
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	624	<pre> Instruction& inst = i; // grab reference to instruction reference<br> Instruction pinst = &i; // grab pointer to instruction reference<br> const Instruction& inst = j;<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	625
				626	<p>However, the iterators you'll be working with in the LLVM framework are
				627	special: they will automatically convert to a ptr-to-instance type whenever they
				628	need to. Instead of dereferencing the iterator and then taking the address of
				629	the result, you can simply assign the iterator to the proper pointer type and
				630	you get the dereference and address-of operation as a result of the assignment
				631	(behind the scenes, this is a result of overloading casting mechanisms). Thus
				632	the last line of the last example,</p>
				633
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	634	<pre>Instruction* pinst = &*i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	635
				636	<p>is semantically equivalent to</p>
				637
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	638	<pre>Instruction* pinst = i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	639
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	640	<p>It's also possible to turn a class pointer into the corresponding iterator,
				641	and this is a constant time operation (very efficient). The following code
				642	snippet illustrates use of the conversion constructors provided by LLVM
				643	iterators. By using these, you can explicitly grab the iterator of something
				644	without actually obtaining it via iteration over some structure:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	645
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	646	<pre>void printNextInstruction(Instruction* inst) {<br> BasicBlock::iterator it(inst);<br> ++it; // after this line, it refers to the instruction after inst.<br> if (it != inst->getParent()->end()) cerr << it << "\n";<br>}<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	647
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	648	</div>
				649
				650	<!--_______________________________________________________________________-->
				651	<div class="doc_subsubsection">
				652	<a name="iterate_complex">Finding call sites: a slightly more complex
				653	example</a>
				654	</div>
				655
				656	<div class="doc_text">
				657
				658	<p>Say that you're writing a FunctionPass and would like to count all the
				659	locations in the entire module (that is, across every <tt>Function</tt>) where a
				660	certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
				661	learn later, you may want to use an <tt>InstVisitor</tt> to accomplish this in a
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	662	much more straight-forward manner, but this example will allow us to explore how
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	663	you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
				664	is what we want to do:</p>
				665
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	666	<pre>initialize callCounter to zero<br>for each Function f in the Module<br> for each BasicBlock b in f<br> for each Instruction i in b<br> if (i is a CallInst and calls the given function)<br> increment callCounter<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	667
				668	<p>And the actual code is (remember, since we're writing a
				669	<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
				670	override the <tt>runOnFunction</tt> method...):</p>
				671
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	672	<pre>Function* targetFunc = ...;<br><br>class OurFunctionPass : public FunctionPass {<br> public:<br> OurFunctionPass(): callCounter(0) { }<br><br> virtual runOnFunction(Function& F) {<br> for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {<br> for (BasicBlock::iterator i = b->begin(); ie = b->end(); i != ie; ++i) {<br> if (<a
				673	href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
				674	href="#CallInst">CallInst</a>>(&*i)) {<br> // we know we've encountered a call instruction, so we<br> // need to determine if it's a call to the<br> // function pointed to by m_func or not.<br> <br> if (callInst->getCalledFunction() == targetFunc)<br> ++callCounter;<br> }<br> }<br> }<br> <br> private:<br> unsigned callCounter;<br>};<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	675
				676	</div>
				677
Brian Gaeke	f1972c6	2003-11-07 19:25:45 +0000	[diff] [blame]	678	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	679	<div class="doc_subsubsection">
				680	<a name="calls_and_invokes">Treating calls and invokes the same way</a>
				681	</div>
				682
				683	<div class="doc_text">
				684
				685	<p>You may have noticed that the previous example was a bit oversimplified in
				686	that it did not deal with call sites generated by 'invoke' instructions. In
				687	this, and in other situations, you may find that you want to treat
				688	<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
				689	most-specific common base class is <tt>Instruction</tt>, which includes lots of
				690	less closely-related things. For these cases, LLVM provides a handy wrapper
				691	class called <a
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	692	href="http://llvm.cs.uiuc.edu/doxygen/classCallSite.html"><tt>CallSite</tt></a>.
				693	It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
				694	methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	695	<tt>InvokeInst</tt>s.</p>
				696
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	697	<p>This class has "value semantics": it should be passed by value, not by
				698	reference and it should not be dynamically allocated or deallocated using
				699	<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
				700	assignable and constructable, with costs equivalents to that of a bare pointer.
				701	If you look at its definition, it has only a single pointer member.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	702
				703	</div>
				704
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	705	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	706	<div class="doc_subsubsection">
				707	<a name="iterate_chains">Iterating over def-use & use-def chains</a>
				708	</div>
				709
				710	<div class="doc_text">
				711
				712	<p>Frequently, we might have an instance of the <a
				713	href="/doxygen/classValue.html">Value Class</a> and we want to determine which
				714	<tt>User</tt>s use the <tt>Value</tt>. The list of all <tt>User</tt>s of a
				715	particular <tt>Value</tt> is called a <i>def-use</i> chain. For example, let's
				716	say we have a <tt>Function*</tt> named <tt>F</tt> to a particular function
				717	<tt>foo</tt>. Finding all of the instructions that <i>use</i> <tt>foo</tt> is as
				718	simple as iterating over the <i>def-use</i> chain of <tt>F</tt>:</p>
				719
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	720	<pre>Function* F = ...;<br><br>for (Value::use_iterator i = F->use_begin(), e = F->use_end(); i != e; ++i) {<br> if (Instruction Inst = dyn_cast<Instruction>(i)) {<br> cerr << "F is used in instruction:\n";<br> cerr << *Inst << "\n";<br> }<br>}<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	721
				722	<p>Alternately, it's common to have an instance of the <a
				723	href="/doxygen/classUser.html">User Class</a> and need to know what
				724	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
				725	<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
				726	<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
				727	all of the values that a particular instruction uses (that is, the operands of
				728	the particular <tt>Instruction</tt>):</p>
				729
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	730	<pre>Instruction* pi = ...;<br><br>for (User::op_iterator i = pi->op_begin(), e = pi->op_end(); i != e; ++i) {<br> Value* v = *i;<br> ...<br>}<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	731
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	732	<!--
				733	def-use chains ("finding all users of"): Value::use_begin/use_end
				734	use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	735	-->
				736
				737	</div>
				738
				739	<!-- ======================================================================= -->
				740	<div class="doc_subsection">
				741	<a name="simplechanges">Making simple changes</a>
				742	</div>
				743
				744	<div class="doc_text">
				745
				746	<p>There are some primitive transformation operations present in the LLVM
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	747	infrastructure that are worth knowing about. When performing
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	748	transformations, it's fairly common to manipulate the contents of basic
				749	blocks. This section describes some of the common methods for doing so
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	750	and gives example code.</p>
				751
				752	</div>
				753
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	754	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	755	<div class="doc_subsubsection">
				756	<a name="schanges_creating">Creating and inserting new
				757	<tt>Instruction</tt>s</a>
				758	</div>
				759
				760	<div class="doc_text">
				761
				762	<p><i>Instantiating Instructions</i></p>
				763
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	764	<p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	765	constructor for the kind of instruction to instantiate and provide the necessary
				766	parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
				767	(const-ptr-to) <tt>Type</tt>. Thus:</p>
				768
				769	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				770
				771	<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
				772	one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
				773	subclass is likely to have varying default parameters which change the semantics
				774	of the instruction, so refer to the <a
				775	href="/doxygen/classInstruction.html">doxygen documentation for the subclass of
				776	Instruction</a> that you're interested in instantiating.</p>
				777
				778	<p><i>Naming values</i></p>
				779
				780	<p>It is very useful to name the values of instructions when you're able to, as
				781	this facilitates the debugging of your transformations. If you end up looking
				782	at generated LLVM machine code, you definitely want to have logical names
				783	associated with the results of instructions! By supplying a value for the
				784	<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
				785	associate a logical name with the result of the instruction's execution at
				786	runtime. For example, say that I'm writing a transformation that dynamically
				787	allocates space for an integer on the stack, and that integer is going to be
				788	used as some kind of index by some other code. To accomplish this, I place an
				789	<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
				790	<tt>Function</tt>, and I'm intending to use it within the same
				791	<tt>Function</tt>. I might do:</p>
				792
				793	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				794
				795	<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
				796	execution value, which is a pointer to an integer on the runtime stack.</p>
				797
				798	<p><i>Inserting instructions</i></p>
				799
				800	<p>There are essentially two ways to insert an <tt>Instruction</tt>
				801	into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
				802
Joel Stanley	9dd1ad6	2002-09-18 03:17:23 +0000	[diff] [blame]	803	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	804	<li>Insertion into an explicit instruction list
				805
				806	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
				807	<tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
				808	before <tt>*pi</tt>, we do the following: </p>
				809
				810	<pre> BasicBlock pb = ...;<br> Instruction pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb<br></pre></li>
				811
				812	<li>Insertion into an implicit instruction list
				813
				814	<p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
				815	are implicitly associated with an existing instruction list: the instruction
				816	list of the enclosing basic block. Thus, we could have accomplished the same
				817	thing as the above code without being given a <tt>BasicBlock</tt> by doing:
				818	</p>
				819
				820	<pre> Instruction pi = ...;<br> Instruction newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
				821
				822	<p>In fact, this sequence of steps occurs so frequently that the
				823	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
				824	constructors which take (as a default parameter) a pointer to an
				825	<tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
				826	precede. That is, <tt>Instruction</tt> constructors are capable of
				827	inserting the newly-created instance into the <tt>BasicBlock</tt> of a
				828	provided instruction, immediately before that instruction. Using an
				829	<tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
				830	parameter, the above code becomes:</p>
				831
				832	<pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
				833
				834	<p>which is much cleaner, especially if you're creating a lot of
				835	instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
				836	</ul>
				837
				838	</div>
				839
				840	<!--_______________________________________________________________________-->
				841	<div class="doc_subsubsection">
				842	<a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
				843	</div>
				844
				845	<div class="doc_text">
				846
				847	<p>Deleting an instruction from an existing sequence of instructions that form a
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	848	<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	849	you must have a pointer to the instruction that you wish to delete. Second, you
				850	need to obtain the pointer to that instruction's basic block. You use the
				851	pointer to the basic block to get its list of instructions and then use the
				852	erase function to remove your instruction. For example:</p>
				853
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	854	<pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
				855	href="#BasicBlock">BasicBlock</a> *BB = I->getParent();<br> BB->getInstList().erase(I);<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	856
				857	</div>
				858
				859	<!--_______________________________________________________________________-->
				860	<div class="doc_subsubsection">
				861	<a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
				862	<tt>Value</tt></a>
				863	</div>
				864
				865	<div class="doc_text">
				866
				867	<p><i>Replacing individual instructions</i></p>
				868
				869	<p>Including "<a href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h</a>"
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	870	permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	871	and <tt>ReplaceInstWithInst</tt>.</p>
				872
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	873	<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	874
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	875	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	876	<li><tt>ReplaceInstWithValue</tt>
				877
				878	<p>This function replaces all uses (within a basic block) of a given
				879	instruction with a value, and then removes the original instruction. The
				880	following example illustrates the replacement of the result of a particular
				881	<tt>AllocaInst</tt> that allocates memory for a single integer with an null
				882	pointer to an integer.</p>
				883
				884	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
				885
				886	<li><tt>ReplaceInstWithInst</tt>
				887
				888	<p>This function replaces a particular instruction with another
				889	instruction. The following example illustrates the replacement of one
				890	<tt>AllocaInst</tt> with another.</p>
				891
				892	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithInst(instToReplace->getParent()->getInstList(), ii,<br> new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));<br></pre></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	893	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	894
				895	<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
				896
				897	<p>You can use <tt>Value::replaceAllUsesWith</tt> and
				898	<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
				899	doxygen documentation for the <a href="/doxygen/classValue.html">Value Class</a>
				900	and <a href="/doxygen/classUser.html">User Class</a>, respectively, for more
				901	information.</p>
				902
				903	<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
				904	include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
				905	ReplaceInstWithValue, ReplaceInstWithInst -->
				906
				907	</div>
				908
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	909	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	910	<div class="doc_section">
				911	<a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
				912	</div>
				913	<!-- *********************************************************************** -->
				914
				915	<div class="doc_text">
				916
				917	<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	918	being inspected or transformed. The core LLVM classes are defined in
				919	header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	920	the <tt>lib/VMCore</tt> directory.</p>
				921
				922	</div>
				923
				924	<!-- ======================================================================= -->
				925	<div class="doc_subsection">
				926	<a name="Value">The <tt>Value</tt> class</a>
				927	</div>
				928
				929	<div>
				930
				931	<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
				932	<br>
				933	doxygen info: <a href="/doxygen/classValue.html">Value Class</a></p>
				934
				935	<p>The <tt>Value</tt> class is the most important class in the LLVM Source
				936	base. It represents a typed value that may be used (among other things) as an
				937	operand to an instruction. There are many different types of <tt>Value</tt>s,
				938	such as <a href="#Constant"><tt>Constant</tt></a>s,<a
				939	href="#Argument"><tt>Argument</tt></a>s. Even <a
				940	href="#Instruction"><tt>Instruction</tt></a>s and <a
				941	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
				942
				943	<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
				944	for a program. For example, an incoming argument to a function (represented
				945	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				946	every instruction in the function that references the argument. To keep track
				947	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				948	href="#User"><tt>User</tt></a>s that is using it (the <a
				949	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				950	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
				951	def-use information in the program, and is accessible through the <tt>use_</tt>*
				952	methods, shown below.</p>
				953
				954	<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
				955	and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				956	method. In addition, all LLVM values can be named. The "name" of the
				957	<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
				958
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	959	<pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	960
				961	<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
				962	that the name of any value may be missing (an empty string), so names should
				963	<b>ONLY</b> be used for debugging (making the source code easier to read,
				964	debugging printouts), they should not be used to keep track of values or map
				965	between them. For this purpose, use a <tt>std::map</tt> of pointers to the
				966	<tt>Value</tt> itself instead.</p>
				967
				968	<p>One important aspect of LLVM is that there is no distinction between an SSA
				969	variable and the operation that produces it. Because of this, any reference to
				970	the value produced by an instruction (or the value available as an incoming
Chris Lattner	d5fc4fc	2004-03-18 14:58:55 +0000	[diff] [blame]	971	argument, for example) is represented as a direct pointer to the instance of
				972	the class that
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	973	represents this value. Although this may take some getting used to, it
				974	simplifies the representation and makes it easier to manipulate.</p>
				975
				976	</div>
				977
				978	<!-- _______________________________________________________________________ -->
				979	<div class="doc_subsubsection">
				980	<a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
				981	</div>
				982
				983	<div class="doc_text">
				984
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	985	<ul>
				986	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the
				987	use-list<br>
				988	<tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
				989	the use-list<br>
				990	<tt>unsigned use_size()</tt> - Returns the number of users of the
				991	value.<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	992	<tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	993	<tt>use_iterator use_begin()</tt> - Get an iterator to the start of
				994	the use-list.<br>
				995	<tt>use_iterator use_end()</tt> - Get an iterator to the end of the
				996	use-list.<br>
				997	<tt><a href="#User">User</a> *use_back()</tt> - Returns the last
				998	element in the list.
				999	<p> These methods are the interface to access the def-use
				1000	information in LLVM. As with all other iterators in LLVM, the naming
				1001	conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1002	</li>
				1003	<li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1004	<p>This method returns the Type of the Value.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1005	</li>
				1006	<li><tt>bool hasName() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1007	<tt>std::string getName() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1008	<tt>void setName(const std::string &Name)</tt>
				1009	<p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
				1010	be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1011	</li>
				1012	<li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1013
				1014	<p>This method traverses the use list of a <tt>Value</tt> changing all <a
				1015	href="#User"><tt>User</tt>s</a> of the current value to refer to
				1016	"<tt>V</tt>" instead. For example, if you detect that an instruction always
				1017	produces a constant value (for example through constant folding), you can
				1018	replace all uses of the instruction with the constant like this:</p>
				1019
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1020	<pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1021	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1022
				1023	</div>
				1024
				1025	<!-- ======================================================================= -->
				1026	<div class="doc_subsection">
				1027	<a name="User">The <tt>User</tt> class</a>
				1028	</div>
				1029
				1030	<div class="doc_text">
				1031
				1032	<p>
				1033	<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1034	doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1035	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1036
				1037	<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
				1038	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				1039	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				1040	referring to. The <tt>User</tt> class itself is a subclass of
				1041	<tt>Value</tt>.</p>
				1042
				1043	<p>The operands of a <tt>User</tt> point directly to the LLVM <a
				1044	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				1045	Single Assignment (SSA) form, there can only be one definition referred to,
				1046	allowing this direct connection. This connection provides the use-def
				1047	information in LLVM.</p>
				1048
				1049	</div>
				1050
				1051	<!-- _______________________________________________________________________ -->
				1052	<div class="doc_subsubsection">
				1053	<a name="m_User">Important Public Members of the <tt>User</tt> class</a>
				1054	</div>
				1055
				1056	<div class="doc_text">
				1057
				1058	<p>The <tt>User</tt> class exposes the operand list in two ways: through
				1059	an index access interface and through an iterator based interface.</p>
				1060
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1061	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1062	<li><tt>Value *getOperand(unsigned i)</tt><br>
				1063	<tt>unsigned getNumOperands()</tt>
				1064	<p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1065	convenient form for direct access.</p></li>
				1066
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1067	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
				1068	list<br>
				1069	<tt>User::op_const_iterator</tt> <tt>use_iterator op_begin()</tt> -
				1070	Get an iterator to the start of the operand list.<br>
				1071	<tt>use_iterator op_end()</tt> - Get an iterator to the end of the
				1072	operand list.
				1073	<p> Together, these methods make up the iterator based interface to
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1074	the operands of a <tt>User</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1075	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1076
				1077	</div>
				1078
				1079	<!-- ======================================================================= -->
				1080	<div class="doc_subsection">
				1081	<a name="Instruction">The <tt>Instruction</tt> class</a>
				1082	</div>
				1083
				1084	<div class="doc_text">
				1085
				1086	<p><tt>#include "</tt><tt><a
				1087	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
				1088	doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
				1089	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1090	href="#Value"><tt>Value</tt></a></p>
				1091
				1092	<p>The <tt>Instruction</tt> class is the common base class for all LLVM
				1093	instructions. It provides only a few methods, but is a very commonly used
				1094	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				1095	opcode (instruction type) and the parent <a
				1096	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				1097	into. To represent a specific type of instruction, one of many subclasses of
				1098	<tt>Instruction</tt> are used.</p>
				1099
				1100	<p> Because the <tt>Instruction</tt> class subclasses the <a
				1101	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				1102	way as for other <a href="#User"><tt>User</tt></a>s (with the
				1103	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				1104	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
				1105	the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
				1106	file contains some meta-data about the various different types of instructions
				1107	in LLVM. It describes the enum values that are used as opcodes (for example
				1108	<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
				1109	concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
				1110	example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				1111	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				1112	this file confuses doxygen, so these enum values don't show up correctly in the
				1113	<a href="/doxygen/classInstruction.html">doxygen output</a>.</p>
				1114
				1115	</div>
				1116
				1117	<!-- _______________________________________________________________________ -->
				1118	<div class="doc_subsubsection">
				1119	<a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
				1120	class</a>
				1121	</div>
				1122
				1123	<div class="doc_text">
				1124
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1125	<ul>
				1126	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1127	<p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
				1128	this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1129	<li><tt>bool mayWriteToMemory()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1130	<p>Returns true if the instruction writes to memory, i.e. it is a
				1131	<tt>call</tt>,<tt>free</tt>,<tt>invoke</tt>, or <tt>store</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1132	<li><tt>unsigned getOpcode()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1133	<p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1134	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1135	<p>Returns another instance of the specified instruction, identical
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1136	in all ways to the original except that the instruction has no parent
				1137	(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1138	and it has no name</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1139	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1140
				1141	</div>
				1142
				1143	<!-- ======================================================================= -->
				1144	<div class="doc_subsection">
				1145	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1146	</div>
				1147
				1148	<div class="doc_text">
				1149
				1150	<p><tt>#include "<a href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1151	doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1152	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1153
				1154	<p>This class represents a single entry multiple exit section of the code,
				1155	commonly known as a basic block by the compiler community. The
				1156	<tt>BasicBlock</tt> class maintains a list of <a
				1157	href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
				1158	Matching the language definition, the last element of this list of instructions
				1159	is always a terminator instruction (a subclass of the <a
				1160	href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
				1161
				1162	<p>In addition to tracking the list of instructions that make up the block, the
				1163	<tt>BasicBlock</tt> class also keeps track of the <a
				1164	href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
				1165
				1166	<p>Note that <tt>BasicBlock</tt>s themselves are <a
				1167	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1168	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1169	<tt>label</tt>.</p>
				1170
				1171	</div>
				1172
				1173	<!-- _______________________________________________________________________ -->
				1174	<div class="doc_subsubsection">
				1175	<a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
				1176	class</a>
				1177	</div>
				1178
				1179	<div class="doc_text">
				1180
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1181	<ul>
				1182	<li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
				1183	href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1184	<p>The <tt>BasicBlock</tt> constructor is used to create new basic
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1185	blocks for insertion into a function. The constructor optionally takes
				1186	a name for the new block, and a <a href="#Function"><tt>Function</tt></a>
				1187	to insert it into. If the <tt>Parent</tt> parameter is specified, the
				1188	new <tt>BasicBlock</tt> is automatically inserted at the end of the
				1189	specified <a href="#Function"><tt>Function</tt></a>, if not specified,
				1190	the BasicBlock must be manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1191	</li>
				1192	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list
				1193	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1194	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1195	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,<tt>size()</tt>,<tt>empty()</tt>,<tt>rbegin()</tt>,<tt>rend()
				1196	- </tt>STL style functions for accessing the instruction list.
				1197	<p> These methods and typedefs are forwarding functions that have
				1198	the same semantics as the standard library methods of the same names.
				1199	These methods expose the underlying instruction list of a basic block in
				1200	a way that is easy to manipulate. To get the full complement of
				1201	container operations (including operations to update the list), you must
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1202	use the <tt>getInstList()</tt> method.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1203	<li><tt>BasicBlock::InstListType &getInstList()</tt>
				1204	<p> This method is used to get access to the underlying container
				1205	that actually holds the Instructions. This method must be used when
				1206	there isn't a forwarding function in the <tt>BasicBlock</tt> class for
				1207	the operation that you would like to perform. Because there are no
				1208	forwarding functions for "updating" operations, you need to use this if
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1209	you want to update the contents of a <tt>BasicBlock</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1210	<li><tt><a href="#Function">Function</a> *getParent()</tt>
				1211	<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1212	the block is embedded into, or a null pointer if it is homeless.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1213	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
				1214	<p> Returns a pointer to the terminator instruction that appears at
				1215	the end of the <tt>BasicBlock</tt>. If there is no terminator
				1216	instruction, or if the last instruction in the block is not a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1217	terminator, then a null pointer is returned.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1218	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1219
				1220	</div>
				1221
				1222	<!-- ======================================================================= -->
				1223	<div class="doc_subsection">
				1224	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1225	</div>
				1226
				1227	<div class="doc_text">
				1228
				1229	<p><tt>#include "<a
				1230	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
				1231	doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
				1232	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1233	href="#Value"><tt>Value</tt></a></p>
				1234
				1235	<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1236	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1237	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1238	Because they are visible at global scope, they are also subject to linking with
				1239	other globals defined in different translation units. To control the linking
				1240	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1241	<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
				1242	defined by the <tt>LinkageTypes</tt> enumerator.</p>
				1243
				1244	<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1245	<tt>static</tt> in C), it is not visible to code outside the current translation
				1246	unit, and does not participate in linking. If it has external linkage, it is
				1247	visible to external code, and does participate in linking. In addition to
				1248	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1249	href="#Module"><tt>Module</tt></a> they are currently part of.</p>
				1250
				1251	<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
				1252	by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
				1253	global is always a pointer to its contents. It is important to remember this
				1254	when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
				1255	be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
				1256	subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
				1257	int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
				1258	the address of the first element of this array and the value of the
				1259	<tt>GlobalVariable</tt> are the same, they have different types. The
				1260	<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
				1261	is <tt>int.</tt> Because of this, accessing a global value requires you to
				1262	dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
				1263	can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
				1264	Language Reference Manual</a>.</p>
				1265
				1266	</div>
				1267
				1268	<!-- _______________________________________________________________________ -->
				1269	<div class="doc_subsubsection">
				1270	<a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
				1271	class</a>
				1272	</div>
				1273
				1274	<div class="doc_text">
				1275
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1276	<ul>
				1277	<li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1278	<tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1279	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
				1280	<p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
				1281	<p> </p>
				1282	</li>
				1283	<li><tt><a href="#Module">Module</a> *getParent()</tt>
				1284	<p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1285	GlobalValue is currently embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1286	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1287
				1288	</div>
				1289
				1290	<!-- ======================================================================= -->
				1291	<div class="doc_subsection">
				1292	<a name="Function">The <tt>Function</tt> class</a>
				1293	</div>
				1294
				1295	<div class="doc_text">
				1296
				1297	<p><tt>#include "<a
				1298	href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
				1299	info: <a href="/doxygen/classFunction.html">Function Class</a><br> Superclasses:
				1300	<a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1301	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1302
				1303	<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1304	actually one of the more complex classes in the LLVM heirarchy because it must
				1305	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1306	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1307	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1308	href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
				1309
				1310	<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
				1311	commonly used part of <tt>Function</tt> objects. The list imposes an implicit
				1312	ordering of the blocks in the function, which indicate how the code will be
				1313	layed out by the backend. Additionally, the first <a
				1314	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1315	<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
				1316	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1317	nodes from a single <tt>Function</tt>. If the <a
				1318	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1319	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1320	function hasn't been linked in yet.</p>
				1321
				1322	<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1323	<tt>Function</tt> class also keeps track of the list of formal <a
				1324	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1325	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1326	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1327	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
				1328
				1329	<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
				1330	LLVM feature that is only used when you have to look up a value by name. Aside
				1331	from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
				1332	internally to make sure that there are not conflicts between the names of <a
				1333	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1334	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1335	href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
				1336
				1337	</div>
				1338
				1339	<!-- _______________________________________________________________________ -->
				1340	<div class="doc_subsubsection">
				1341	<a name="m_Function">Important Public Members of the <tt>Function</tt>
				1342	class</a>
				1343	</div>
				1344
				1345	<div class="doc_text">
				1346
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1347	<ul>
				1348	<li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1349	Ty, bool isInternal, const std::string &N = "", Module Parent = 0)</tt>
				1350
				1351	<p>Constructor used when you need to create new <tt>Function</tt>s to add
				1352	the the program. The constructor must specify the type of the function to
				1353	create and whether or not it should start out with internal or external
				1354	linkage. The <a href="#FunctionType"><tt>FunctionType</tt></a> argument
				1355	specifies the formal arguments and return value for the function. The same
				1356	<a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
				1357	create multiple functions. The <tt>Parent</tt> argument specifies the Module
				1358	in which the function is defined. If this argument is provided, the function
				1359	will automatically be inserted into that module's list of
				1360	functions.</p></li>
				1361
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1362	<li><tt>bool isExternal()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1363
				1364	<p>Return whether or not the <tt>Function</tt> has a body defined. If the
				1365	function is "external", it does not have a body, and thus must be resolved
				1366	by linking with a function defined in a different translation unit.</p></li>
				1367
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1368	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1369	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1370
				1371	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1372	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1373
				1374	<p>These are forwarding methods that make it easy to access the contents of
				1375	a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1376	list.</p></li>
				1377
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1378	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1379
				1380	<p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
				1381	is necessary to use when you need to update the list or perform a complex
				1382	action that doesn't have a forwarding method.</p></li>
				1383
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1384	<li><tt>Function::aiterator</tt> - Typedef for the argument list
				1385	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1386	<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1387
				1388	<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
				1389	<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt>
				1390
				1391	<p>These are forwarding methods that make it easy to access the contents of
				1392	a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
				1393	list.</p></li>
				1394
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1395	<li><tt>Function::ArgumentListType &getArgumentList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1396
				1397	<p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1398	necessary to use when you need to update the list or perform a complex
				1399	action that doesn't have a forwarding method.</p></li>
				1400
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1401	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1402
				1403	<p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1404	function. Because the entry block for the function is always the first
				1405	block, this returns the first block of the <tt>Function</tt>.</p></li>
				1406
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1407	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1408	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1409
				1410	<p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
				1411	<tt>Function</tt> and returns the return type of the function, or the <a
				1412	href="#FunctionType"><tt>FunctionType</tt></a> of the actual
				1413	function.</p></li>
				1414
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1415	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1416
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1417	<p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1418	for this <tt>Function</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1419	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1420
				1421	</div>
				1422
				1423	<!-- ======================================================================= -->
				1424	<div class="doc_subsection">
				1425	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1426	</div>
				1427
				1428	<div class="doc_text">
				1429
				1430	<p><tt>#include "<a
				1431	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
				1432	<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1433	doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1434	Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1435	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1436
				1437	<p>Global variables are represented with the (suprise suprise)
				1438	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
				1439	subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
				1440	always referenced by their address (global values must live in memory, so their
				1441	"name" refers to their address). See <a
				1442	href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
				1443	may have an initial value (which must be a <a
				1444	href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
				1445	may be marked as "constant" themselves (indicating that their contents never
				1446	change at runtime).</p>
				1447
				1448	</div>
				1449
				1450	<!-- _______________________________________________________________________ -->
				1451	<div class="doc_subsubsection">
				1452	<a name="m_GlobalVariable">Important Public Members of the
				1453	<tt>GlobalVariable</tt> class</a>
				1454	</div>
				1455
				1456	<div class="doc_text">
				1457
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1458	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1459	<li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
				1460	isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
				1461	Initializer = 0, const std::string &Name = "", Module Parent = 0)</tt>
				1462
				1463	<p>Create a new global variable of the specified type. If
				1464	<tt>isConstant</tt> is true then the global variable will be marked as
				1465	unchanging for the program. The Linkage parameter specifies the type of
				1466	linkage (internal, external, weak, linkonce, appending) for the variable. If
				1467	the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,  then
				1468	the resultant global variable will have internal linkage. AppendingLinkage
				1469	concatenates together all instances (in different translation units) of the
				1470	variable into a single variable but is only applicable to arrays.  See
				1471	the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
				1472	further details on linkage types. Optionally an initializer, a name, and the
				1473	module to put the variable into may be specified for the global variable as
				1474	well.</p></li>
				1475
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1476	<li><tt>bool isConstant() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1477
				1478	<p>Returns true if this is a global variable that is known not to
				1479	be modified at runtime.</p></li>
				1480
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1481	<li><tt>bool hasInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1482
				1483	<p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
				1484
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1485	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1486
				1487	<p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
				1488	to call this method if there is no initializer.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1489	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1490
				1491	</div>
				1492
				1493	<!-- ======================================================================= -->
				1494	<div class="doc_subsection">
				1495	<a name="Module">The <tt>Module</tt> class</a>
				1496	</div>
				1497
				1498	<div class="doc_text">
				1499
				1500	<p><tt>#include "<a
				1501	href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
				1502	<a href="/doxygen/classModule.html">Module Class</a></p>
				1503
				1504	<p>The <tt>Module</tt> class represents the top level structure present in LLVM
				1505	programs. An LLVM module is effectively either a translation unit of the
				1506	original program or a combination of several translation units merged by the
				1507	linker. The <tt>Module</tt> class keeps track of a list of <a
				1508	href="#Function"><tt>Function</tt></a>s, a list of <a
				1509	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1510	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1511	helpful member functions that try to make common operations easy.</p>
				1512
				1513	</div>
				1514
				1515	<!-- _______________________________________________________________________ -->
				1516	<div class="doc_subsubsection">
				1517	<a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
				1518	</div>
				1519
				1520	<div class="doc_text">
				1521
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1522	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1523	<li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1524	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1525
				1526	<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
				1527	provide a name for it (probably based on the name of the translation unit).</p>
				1528
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1529	<ul>
				1530	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1531	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1532
				1533	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1534	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1535
				1536	<p>These are forwarding methods that make it easy to access the contents of
				1537	a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				1538	list.</p></li>
				1539
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1540	<li><tt>Module::FunctionListType &getFunctionList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1541
				1542	<p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				1543	necessary to use when you need to update the list or perform a complex
				1544	action that doesn't have a forwarding method.</p>
				1545
				1546	<p><!-- Global Variable --></p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1547	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1548
				1549	<hr>
				1550
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1551	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1552	<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
				1553
				1554	<tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
				1555
				1556	<tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
				1557	<tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt>
				1558
				1559	<p> These are forwarding methods that make it easy to access the contents of
				1560	a <tt>Module</tt> object's <a
				1561	href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
				1562
				1563	<li><tt>Module::GlobalListType &getGlobalList()</tt>
				1564
				1565	<p>Returns the list of <a
				1566	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
				1567	use when you need to update the list or perform a complex action that
				1568	doesn't have a forwarding method.</p>
				1569
				1570	<p><!-- Symbol table stuff --> </p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1571	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1572
				1573	<hr>
				1574
				1575	<ul>
				1576	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
				1577
				1578	<p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1579	for this <tt>Module</tt>.</p>
				1580
				1581	<p><!-- Convenience methods --></p></li>
				1582	</ul>
				1583
				1584	<hr>
				1585
				1586	<ul>
				1587	<li><tt><a href="#Function">Function</a> *getFunction(const std::string
				1588	&Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
				1589
				1590	<p>Look up the specified function in the <tt>Module</tt> <a
				1591	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				1592	<tt>null</tt>.</p></li>
				1593
				1594	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
				1595	std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
				1596
				1597	<p>Look up the specified function in the <tt>Module</tt> <a
				1598	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				1599	external declaration for the function and return it.</p></li>
				1600
				1601	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
				1602
				1603	<p>If there is at least one entry in the <a
				1604	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				1605	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				1606	string.</p></li>
				1607
				1608	<li><tt>bool addTypeName(const std::string &Name, const <a
				1609	href="#Type">Type</a> *Ty)</tt>
				1610
				1611	<p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1612	mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
				1613	name, true is returned and the <a
				1614	href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
				1615	</ul>
				1616
				1617	</div>
				1618
				1619	<!-- ======================================================================= -->
				1620	<div class="doc_subsection">
				1621	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				1622	</div>
				1623
				1624	<div class="doc_text">
				1625
				1626	<p>Constant represents a base class for different types of constants. It
				1627	is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				1628	ConstantArray etc for representing the various types of Constants.</p>
				1629
				1630	</div>
				1631
				1632	<!-- _______________________________________________________________________ -->
				1633	<div class="doc_subsubsection">
				1634	<a name="m_Value">Important Public Methods</a>
				1635	</div>
				1636
				1637	<div class="doc_text">
				1638
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1639	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1640	<li><tt>bool isConstantExpr()</tt>: Returns true if it is a
				1641	ConstantExpr
				1642	<hr> Important Subclasses of Constant
				1643	<p> </p>
				1644	<ul>
				1645	<li>ConstantSInt : This subclass of Constant represents a signed
				1646	integer constant.
				1647	<ul>
				1648	<li><tt>int64_t getValue() const</tt>: Returns the underlying value of
				1649	this constant. </li>
				1650	</ul>
				1651	</li>
				1652	<li>ConstantUInt : This class represents an unsigned integer.
				1653	<ul>
				1654	<li><tt>uint64_t getValue() const</tt>: Returns the underlying value
				1655	of this constant. </li>
				1656	</ul>
				1657	</li>
				1658	<li>ConstantFP : This class represents a floating point constant.
				1659	<ul>
				1660	<li><tt>double getValue() const</tt>: Returns the underlying value of
				1661	this constant. </li>
				1662	</ul>
				1663	</li>
				1664	<li>ConstantBool : This represents a boolean constant.
				1665	<ul>
				1666	<li><tt>bool getValue() const</tt>: Returns the underlying value of
				1667	this constant. </li>
				1668	</ul>
				1669	</li>
				1670	<li>ConstantArray : This represents a constant array.
				1671	<ul>
				1672	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1673	Returns a Vecotr of component constants that makeup this array. </li>
				1674	</ul>
				1675	</li>
				1676	<li>ConstantStruct : This represents a constant struct.
				1677	<ul>
				1678	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1679	Returns a Vecotr of component constants that makeup this array. </li>
				1680	</ul>
				1681	</li>
				1682	<li>ConstantPointerRef : This represents a constant pointer value
				1683	that is initialized to point to a global value, which lies at a
				1684	constant fixed address.
				1685	<ul>
				1686	<li><tt>GlobalValue *getValue()</tt>: Returns the global
				1687	value to which this pointer is pointing to. </li>
				1688	</ul>
				1689	</li>
				1690	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1691	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1692	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1693
				1694	</div>
				1695
				1696	<!-- ======================================================================= -->
				1697	<div class="doc_subsection">
				1698	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				1699	</div>
				1700
				1701	<div class="doc_text">
				1702
				1703	<p>Type as noted earlier is also a subclass of a Value class. Any primitive
				1704	type (like int, short etc) in LLVM is an instance of Type Class. All other
				1705	types are instances of subclasses of type like FunctionType, ArrayType
				1706	etc. DerivedType is the interface for all such dervied types including
				1707	FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
				1708	be recursive (StructType). There exists exactly one instance of any type
				1709	structure at a time. This allows using pointer equality of Type *s for comparing
				1710	types.</p>
				1711
				1712	</div>
				1713
				1714	<!-- _______________________________________________________________________ -->
				1715	<div class="doc_subsubsection">
				1716	<a name="m_Value">Important Public Methods</a>
				1717	</div>
				1718
				1719	<div class="doc_text">
				1720
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1721	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1722
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1723	<li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
				1724	is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
				1725	not true for Float and Double. </li>
				1726
				1727	<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
				1728	unsigned. This is not quite the complement of isSigned... nonnumeric types
				1729	return false as they do with isSigned. This returns true for UByteTy,
				1730	UShortTy, UIntTy, and ULongTy. </li>
				1731
				1732	<li><tt>bool isInteger() const</tt>: Equilivent to isSigned() \|\| isUnsigned(),
				1733	but with only a single virtual function invocation.</li>
				1734
				1735	<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
				1736	type, which is either Bool type or one of the Integer types.</li>
				1737
				1738	<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
				1739	floating point types.</li>
				1740
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1741	<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
				1742	this type can be converted to 'Ty' without any reinterpretation of bits. For
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	1743	example, uint to int or one pointer type to another.</li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1744
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	1745	<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1746	<p>Derived Types</p>
				1747
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1748	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1749	<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1750	<ul>
				1751	<li><tt>const Type * getElementType() const</tt>: Returns the type of
				1752	each of the elements in the sequential type. </li>
				1753	</ul>
				1754	</li>
				1755	<li>ArrayType : This is a subclass of SequentialType and defines
				1756	interface for array types.
				1757	<ul>
				1758	<li><tt>unsigned getNumElements() const</tt>: Returns the number of
				1759	elements in the array. </li>
				1760	</ul>
				1761	</li>
				1762	<li>PointerType : Subclass of SequentialType for pointer types. </li>
				1763	<li>StructType : subclass of DerivedTypes for struct types </li>
				1764	<li>FunctionType : subclass of DerivedTypes for function types.
				1765	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1766	<li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
				1767	function</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1768	<li><tt> const Type * getReturnType() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1769	return type of the function.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1770	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1771	the type of the ith parameter.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1772	<li><tt> const unsigned getNumParams() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1773	number of formal parameters.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1774	</ul>
				1775	</li>
				1776	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1777	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1778	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1779
				1780	</div>
				1781
				1782	<!-- ======================================================================= -->
				1783	<div class="doc_subsection">
				1784	<a name="Argument">The <tt>Argument</tt> class</a>
				1785	</div>
				1786
				1787	<div class="doc_text">
				1788
				1789	<p>This subclass of Value defines the interface for incoming formal
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1790	arguments to a function. A Function maitanis a list of its formal
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1791	arguments. An argument has a pointer to the parent Function.</p>
				1792
				1793	</div>
				1794
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame^]	1795	<!-- ======================================================================= -->
				1796	<div class="doc_subsection">
				1797	<a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
				1798	</div>
				1799	<div class="doc_text">
				1800	<p>This class provides a symbol table that the
				1801	<a href="#Function"><tt>Function</tt></a> and <a href="#Module">
				1802	<tt>Module</tt></a> classes use for naming definitions. The symbol table can
				1803	provide a name for any <a href="#Value"><tt>Value</tt></a> or
				1804	<a href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
				1805	type. It hides the data it contains and provides access to it through a
				1806	controlled interface.</p>
				1807
				1808	<p>To use the <tt>SymbolTable</tt> well, you need to understand the
				1809	structure of the information it holds. The class contains two
				1810	<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
				1811	<tt>Type</tt> to maps of name (<tt>std::string</tt>) to <tt>Value</tt>.
				1812	The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
				1813	are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
				1814	however, are stored in a single dimension and accessed only by name.</p>
				1815
				1816	<p>The interface of this class provides three basic types of operations:
				1817	<ol>
				1818	<li><em>Accessors</em>. Accessors provide read-only access to information
				1819	such as finding a value for a name with the
				1820	<a href="#SymbolTable_lookup">lookup</a> method.</li>
				1821	<li><em>Mutators</em>. Mutators allow the user to add information to the
				1822	<tt>SymbolTable</tt> with methods like
				1823	<a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
				1824	<li><em>Iterators</em>. Iterators allow the user to traverse the content
				1825	of the symbol table in well defined ways, such as the method
				1826	<a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
				1827	</ol>
				1828
				1829	<h3>Accessors</h3>
				1830	<dl>
				1831	<dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
				1832	</dt>
				1833	<dd>The <tt>lookup</tt> method searches the type plane given by the
				1834	<tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
				1835	If a suitable <tt>Value</tt> is not found, null is returned.</dd>
				1836
				1837	<dt><tt>Type* lookupType( const std::string& name) const</tt>:</dt>
				1838	<dd>The <tt>lookupType</tt> method searches through the types for a
				1839	<tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
				1840	is not found, null is returned.</dd>
				1841
				1842	<dt><tt>bool hasTypes() const</tt>:</dt>
				1843	<dd>This function returns true if an entry has been made into the type
				1844	map.</dd>
				1845
				1846	<dt><tt>bool isEmpty() const</tt>:</dt>
				1847	<dd>This function returns true if both the value and types maps are
				1848	empty</dd>
				1849
				1850	<dt><tt>std::string get_name(const Value*) const</tt>:</dt>
				1851	<dd>This function returns the name of the Value provided or the empty
				1852	string if the Value is not in the symbol table.</dd>
				1853
				1854	<dt><tt>std::string get_name(const Type*) const</tt>:</dt>
				1855	<dd>This function returns the name of the Type provided or the empty
				1856	string if the Type is not in the symbol table.</dd>
				1857	</dl>
				1858
				1859	<h3>Mutators</h3>
				1860	<dl>
				1861	<dt><tt>void insert(Value *Val)</tt>:</dt>
				1862	<dd>This method adds the provided value to the symbol table. The Value must
				1863	have both a name and a type which are extracted and used to place the value
				1864	in the correct type plane under the value's name.</dd>
				1865
				1866	<dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
				1867	<dd> Inserts a constant or type into the symbol table with the specified
				1868	name. There can be a many to one mapping between names and constants
				1869	or types.</dd>
				1870
				1871	<dt><tt>void insert(const std::string& Name, Type *Typ)</tt>:</dt>
				1872	<dd> Inserts a type into the symbol table with the specified name. There
				1873	can be a many-to-one mapping between names and types. This method
				1874	allows a type with an existing entry in the symbol table to get
				1875	a new name.</dd>
				1876
				1877	<dt><tt>void remove(Value* Val)</tt>:</dt>
				1878	<dd> This method removes a named value from the symbol table. The
				1879	type and name of the Value are extracted from \p N and used to
				1880	lookup the Value in the correct type plane. If the Value is
				1881	not in the symbol table, this method silently ignores the
				1882	request.</dd>
				1883
				1884	<dt><tt>void remove(Type* Typ)</tt>:</dt>
				1885	<dd> This method removes a named type from the symbol table. The
				1886	name of the type is extracted from \P T and used to look up
				1887	the Type in the type map. If the Type is not in the symbol
				1888	table, this method silently ignores the request.</dd>
				1889
				1890	<dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
				1891	<dd> Remove a constant or type with the specified name from the
				1892	symbol table.</dd>
				1893
				1894	<dt><tt>Type* remove(const std::string& Name, Type* T)</tt>:</dt>
				1895	<dd> Remove a type with the specified name from the symbol table.
				1896	Returns the removed Type.</dd>
				1897
				1898	<dt><tt>Value *value_remove(const value_iterator& It)</tt>:</dt>
				1899	<dd> Removes a specific value from the symbol table.
				1900	Returns the removed value.</dd>
				1901
				1902	<dt><tt>bool strip()</tt>:</dt>
				1903	<dd> This method will strip the symbol table of its names leaving
				1904	the type and values. </dd>
				1905
				1906	<dt><tt>void clear()</tt>:</dt>
				1907	<dd>Empty the symbol table completely.</dd>
				1908	</dl>
				1909
				1910	<h3>Iteration</h3>
				1911	<p>The following functions describe three types of iterators you can obtain
				1912	the beginning or end of the sequence for both const and non-const. It is
				1913	important to keep track of the different kinds of iterators. There are
				1914	three idioms worth pointing out:</p>
				1915	<table class="doc_table">
				1916	<tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
				1917	<tr>
				1918	<td>Planes Of name/Value maps</td><td>PI</td>
				1919	<td><tt><pre>
				1920	for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
				1921	PE = ST.plane_end(); PI != PE; ++PI ) {
				1922	PI->first // This is the Type* of the plane
				1923	PI->second // This is the SymbolTable::ValueMap of name/Value pairs
				1924	</pre></tt></td>
				1925	</tr>
				1926	<tr>
				1927	<td>All name/Type Pairs</td><td>TI</td>
				1928	<td><tt><pre>
				1929	for (SymbolTable::type_const_iterator TI = ST.type_begin(),
				1930	TE = ST.type_end(); TI != TE; ++TI )
				1931	TI->first // This is the name of the type
				1932	TI->second // This is the Type* value associated with the name
				1933	</pre></tt></td>
				1934	</tr>
				1935	<tr>
				1936	<td>name/Value pairs in a plane</td><td>VI</td>
				1937	<td><tt><pre>
				1938	for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
				1939	VE = ST.value_end(SomeType); VI != VE; ++VI )
				1940	VI->first // This is the name of the Value
				1941	VI->second // This is the Value* value associated with the name
				1942	</pre></tt></td>
				1943	</tr>
				1944	</table>
				1945	<p>Using the recommended iterator names and idioms will help you avoid
				1946	making mistakes. Of particular note, make sure that whenever you use
				1947	value_begin(SomeType) that you always compare the resulting iterator
				1948	with value_end(SomeType) not value_end(SomeOtherType) or else you
				1949	will loop infinitely.</p>
				1950
				1951	<dl>
				1952
				1953	<dt><tt>plane_iterator plane_begin()</tt>:</dt>
				1954	<dd>Get an iterator that starts at the beginning of the type planes.
				1955	The iterator will iterate over the Type/ValueMap pairs in the
				1956	type planes. </dd>
				1957
				1958	<dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
				1959	<dd>Get a const_iterator that starts at the beginning of the type
				1960	planes. The iterator will iterate over the Type/ValueMap pairs
				1961	in the type planes. </dd>
				1962
				1963	<dt><tt>plane_iterator plane_end()</tt>:</dt>
				1964	<dd>Get an iterator at the end of the type planes. This serves as
				1965	the marker for end of iteration over the type planes.</dd>
				1966
				1967	<dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
				1968	<dd>Get a const_iterator at the end of the type planes. This serves as
				1969	the marker for end of iteration over the type planes.</dd>
				1970
				1971	<dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
				1972	<dd>Get an iterator that starts at the beginning of a type plane.
				1973	The iterator will iterate over the name/value pairs in the type plane.
				1974	Note: The type plane must already exist before using this.</dd>
				1975
				1976	<dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
				1977	<dd>Get a const_iterator that starts at the beginning of a type plane.
				1978	The iterator will iterate over the name/value pairs in the type plane.
				1979	Note: The type plane must already exist before using this.</dd>
				1980
				1981	<dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
				1982	<dd>Get an iterator to the end of a type plane. This serves as the marker
				1983	for end of iteration of the type plane.
				1984	Note: The type plane must already exist before using this.</dd>
				1985
				1986	<dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
				1987	<dd>Get a const_iterator to the end of a type plane. This serves as the
				1988	marker for end of iteration of the type plane.
				1989	Note: the type plane must already exist before using this.</dd>
				1990
				1991	<dt><tt>type_iterator type_begin()</tt>:</dt>
				1992	<dd>Get an iterator to the start of the name/Type map.</dd>
				1993
				1994	<dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
				1995	<dd> Get a const_iterator to the start of the name/Type map.</dd>
				1996
				1997	<dt><tt>type_iterator type_end()</tt>:</dt>
				1998	<dd>Get an iterator to the end of the name/Type map. This serves as the
				1999	marker for end of iteration of the types.</dd>
				2000
				2001	<dt><tt>type_const_iterator type_end() const</tt>:</dt>
				2002	<dd>Get a const-iterator to the end of the name/Type map. This serves
				2003	as the marker for end of iteration of the types.</dd>
				2004
				2005	<dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
				2006	<dd>This method returns a plane_const_iterator for iteration over
				2007	the type planes starting at a specific plane, given by \p Ty.</dd>
				2008
				2009	<dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
				2010	<dd>This method returns a plane_iterator for iteration over the
				2011	type planes starting at a specific plane, given by \p Ty.</dd>
				2012
				2013	<dt><tt>const ValueMap* findPlane( const Type* Typ ) cons</tt>:</dt>
				2014	<dd>This method returns a ValueMap* for a specific type plane. This
				2015	interface is deprecated and may go away in the future.</dd>
				2016	</dl>
				2017	</div>
				2018
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	2019	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2020	<hr>
				2021	<address>
				2022	<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
				2023	src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
				2024	<a href="http://validator.w3.org/check/referer"><img
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				2026
				2027	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				2028	<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
				2029	<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
				2030	Last modified: $Date$
				2031	</address>
				2032
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2033	</body>
				2034	</html>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame^]	2035	<!-- vim: sw=2 noai
				2036	-->